Polymerase chain reaction (PCR) assays are generally used for molecular diagnostics due to the sensitivity and specificity of the assay. PCR is a technique which allows a single copy or piece of DNA to be replicated, amplifying the amount of DNA in a sample to be analyzed. In this manner, even single nucleotide changes can be detected through well-constructed PCR assays. PCR generally involves thermal cycling of a sample, e.g. repeated heating and cooling of the sample, to allow for DNA melting and enzymatic replication. The thermal cycling generally takes place in the presence of PCR reagents. PCR reagents generally include primers (e.g. DNA fragments complementary to a target region of interest) and DNA polymerase.
Systems are available for performing PCR with purified nucleic acid inputs. Non-disk-based microfluidic devices integrating sample preparation with amplification and detection exist. The sample input generally requires purified cell populations from culture, suspended in buffers such as PBS; environmental samples often important for biodefense are unable to be analyzed on the platform. Commercial systems for analysis of clinical samples by PCR on microfluidic systems are available. These systems typically require extensive sample preparation before introduction into the system.